Process of neutralizing acid treated lubricating oil distillates and the like



Patented Jan. 13, 1942 PROCESS OF NEUTRALIZING ACID TREATED LUBRICATINGOIL DISTILLATES AND THE LIKE Arthur E. Catanach and Eric Kolthoff, PortArthur, Tex., assignors to Gulf Oil Corporation, Pittsburgh, Pa., acorporation of Pennsylvania No Drawing. Application January 15, 1940,Serial No. 313,972

Claims.

This invention relates to animproved process of neutralizing acidtreated lubricating oil distillates and the like; and it comprisesintimately contacting an acid treated lubricating oil distillate or thelike with just sufiicient caustic, soda solution to substantiallyneutralize the mineral acid content thereof, treating the resultingpar.- tially neutralized oil with an agent adapted to settle out themineral salts and soaps, and-then intimately contacting the oil withcaustic. soda solution in quantity suflicient to neutralize the organicacidity present therein; all as. more fully hereinafter set forth and asclaimed.

Certain lubricating oils and other petroleum distillates of similarviscosity and boiling range, e. g. transformer oil, have a high acidiccontent. This is particularly true of oils having an as.- phaltic ornaphthenic base. After the usual refining step of sulfuric acidtreatment, such oils have an even higher acidity. It. is essential toreduce this acidity to avoid corrosion of. materials in contact with theoils.

A scale adopted by the American Society for Testing Materials which isin wide useisknown as A. S. T. M. D 188-2'7T. In termsof thisscale, afinished lubricating oil should not havea. neutralization number or acidnumber ofmore than about 0.05. Unfinished oils of the type discussedabove, however, may haveconsiderably higher neutralization numbers, e.g. as much as 2.50 before acid treatment.

It is therefore common practice to neutralize these oils. One methodof'doing this consists of adding caustic soda solution to stills duringdistillation of crude petroleum. This is disadvantageous for at leasttwo reasons. In the first place, the caustic solution may cause corroiQn of distillation equipment. In the second place, such a method isundesirable or impossible. where it is desired to recover the asphaltbottoms because the latter must be substantially free from ash andalkali.

Another common practice is to neutralize. the oil with caustic sodasolution until it is just alkalin to phenolphthalein; thisindicatesneutralization of organic as well as mineral acidity. However,particularly in the case of an oil having a large amount of organicacidity, a stable emulsion generally results, which is extremelydiflicult to break. In fact; the difiiculty of neutralizingacid treatedlubricatingv oil and the like derived from high neutralization numberpetroleum distillates has been sogreat that it iscommon practice torelegate these distillates to fuel oil and cracking purposes without anychemical refining.

A further particular instance of the costliness of neutralizing acidtreated oils derived from high neutralization number distillates is therefining of white oil. White oil requires heavy treatment withconcentrated sulfuric acid and the. acid treated product requiresneutralization. It is common practice to avoid emulsions by neutralizingwith caustioized methyl alcohol. That this is a costly process isobvious to anyone skilled in the art.

It is an achieved object of this invention to neutralize acid treatedlubricating oils and the like, and particularly those derived from highneutralization number petroleum distillates, withoutformation ofemulsions.

We have found that acid treated lubricating oils and the like can beneutralized without the formation of emulsionsby contacting th oil withcaustic soda solution in quantity just suflicient to substantially.neutralize the mineral acidity, treating the thus, partiallyneutralizedoil with. an agent adapted to settle out the mineralsalts and soaps, andcontacting the resulting oil witlicaustic soda solution in quantity sucient to] neu. tralize the organic acidity.

This processmay be appliedtomotor lubricating stocks, transformeroils,White oils. andfthe like. Various. settling agents such as] are commonlyused as demulsifiers may be used for set} tling out mineral salts andsoaps. We have had particularly good results with rosin soap. Manycompositions known as Tret-O-Lite compounds may also be used.Tret-O-Lite is a trade'naine applied to a class ofdemulsifying agentsWell known in the petroleum industry for their use in the Tret-O-Liteprocess, which is aprocess for breaking water-in-oil emulsions.

Various means of carry ng. out the procedure of this invention may beemployed. Howeve we findthe following to be particularly advantageous:

A sample from a batch ofoil to be. neutralized is analyzed to determine(1.) the mineral acidity, and (2) the organic acidity. This can be can;veniently done by shaking the sample withfsliiall quantities ofstandardized caustic soda solution until it is just alkaline to methylorange, thus indicating the mineral acidity, and then shaking withfurther quantities of standardized caustic soda solution until it isjust alkaline tophenol phthalein, thus indicating theorganic acidity.The main batch is then agitated with"sufiiclent caustic soda solution ofabout 34 Re. to neutralize about per cent of its mineral acidity and theremaining mineral acidity 'is neutralized with 5 to 10 B. caustic sodasolution. The partially neutralized oil is then agitated with a rosinsoap solution and the aqueous layer is allowed to separate and is drawnoil. The oil is then agitated with caustic soda solution of about 34 Be.until it i just alkaline to phenolphthalein and the aqueous layer issettled and drawn off. The oil is then given a final wash with water toremove traces of alkali and is given a conventional brighteningtreatment, e. g. by blowing air through it.

It is advantageous to employ a relatively concentrated caustic sodasolution such as 34 Be. for the bulk of the first neutralization stepinstead of a dilute solution because more rapid settling results and therosin soap solution is not overly diluted and can be used repeatedly. Itis advantageous to finish ofi the remainder of this neutralization stepwith a more dilute solution such as a 5 to B. caustic soda solution Ibecause a more accurate control of the end point is thereby madepossible. The use of relatively concentrated caustic soda such as 34 B.in the second neutralization step is advantageous because of its rapidsettling effect. a

We have found that the use of a settling agent, particularly rosin soap,between the first and second neutralization steps is essential to removesludge pepper and to eifect a settling out of the mineral salts andsoaps formed in the first neutralization step without the necessity ofemploying high temperatures. In the absence of this intermediatesettling step employing a settling agent such as rosin soap, it may benecessary to employ high temperatures to effect settling of the aqueouslayer and break emulsions. Thus in one prior art process lubricatingstock is partially neutralized with caustic soda solution at atemperature of 150 to 180 F. and is then, after drawing off the aqueouslayer, treated at a temperature of 250 to 280 F. with sufficient causticpotash solution to complete the neutralization. The high temperaturesemployed in this process result in a darkened oil, which is undesirablefrom a commercial point of view. Our process, however, requires noheating during the neutralization steps, and need not involve hea ing toa temperature above about 160 F. at any stage. As a result, an oillighter in color and hence less objectionable as a commercial product isproduced.

The following specific example will serve to illustrate the procedure ofthis invention:

1700 barrels of a sulfuric acid treated lu brieating oil derived byconventional vacuum distillation from Gulf coastal crude was treated.Before acid treatment this lubricating oil had a neutralization numberof 2.10. A sample of the acid treated oil was shaken with standardizedcaustic soda solution until it was just alkaline to methyl orange butstill acid to phenolphthalein, and then with further quantities ofstandardized caustc soda solution until it was just alkaline tophenolphthalein. By this procedure it was found that 1700 barrels ofacid treated oil required 357 pounds of caustic soda to neutralize themineral or methyl orange acidity and 814 pounds to neutralize theorganic or phenolphthalein acidity. 107 gallons of 34 Be. caustic sodasolution were added to the oil with Vigorous agitation of the mixture.This operation neutralized 90 per cent of the mineral or methyl orangeacidity. Then 133 gallons of 5 B.

caustic soda solution were added thus completing the neutralization ofthe mineral acidity.

The oil-water mixture was heated by closed steam to about 160 F. and 200barrels of rosin soap solution made up according to the formula, 1barrel dry rosin soap per 36 barrels of water, were added while air wasblown in to effect agitation. The mixture was allowed to stand for about10 hours when a well defined aqueous layer was formed and there was noemulsion present in either phase. The bottom aqueous layer was drawn offand was used in settling out salts from subsequent batches of partlyneutralized oil. The oily layer was then treated with 271 gallons of 34"A B. caustic soda solution, thereby taking it to the phenolphthalein endpoint and neutralizing the organic acidity. Agitation was providedduring this step. An aqueous layer separated upon allowing the oil tostand a short while and it was drawn off. The oil was then given a washwith water to remove traces of caustic soda and was blown with air tobrighten it. The resulting oil was entirely free from emulsion and had aneutralization number less than 0.05.

Although this invention has been specifically described in the form ofcertain embodiments, it is by no means limited to such embodiments butmay be practiced with many variations within the scope of the appendedclaims.

What we claim is:

1. An improved process of neutralizing an acid treated oil of thelubricating type, derived from a petroleum distillate of highneutralization number, which comprises substantially neutralizing themineral acidity of said oil without neutralizing the organic aciditythereof by means of caustic soda solution, treating the partiallyneutralized oil with a rosin soap solution to settle out mineral saltsand. soaps therefrom, and neutralizing the organic acidity of said oilwith caustic soda solution.

2. An improved process of neutralizing an acid treated oil of thelubricating type, derived from a petroleum distillate of highneutralization number, which comprises substantially neutralizing themineral acidity of said oil without neutralizing the organic aciditythereof by means of caustic soda solution, heating said oil to atemperature between 140 F. and 160 F. and treating it with a rosin soapsolution to settle out mineral salts and soaps therefrom, andneutralizing the organic acidity of said oil with caustic soda solution.

3. An improved process of neutralizing an acid treated oil of thelubricating type, derived from a petroleum distillate of highneutralization numher, which comprises treating said oil with arelatively concentrated caustic soda solution until about 80 to per centof the mineral acidity has been neutralized, neutralizing the remainingmineral acidity with a relatively dilute caustic soda solution, treatingthe thus neutralized oil with a rosin soap solution to settle outmineral salts and soaps therefrom, and neutralizing the organic acidityof said oil with caustic soda soluti-on.

4. An improved process of neutralizing an acid treated oil of thelubricating type, derived from a petroleum distillate of highneutralization number, which comprises treating said oil with arelatively concentrated caustic soda solution until about 80 to 90 percent of the mineral acidity has been neutralized, neutralizing theremaining mineral acidity with a relatively dilute caustic sodasolution, heating said oil to a temperature between 140 F. and 160 F.and treating it with a rosin soap solution to settle out mineral saltsand soaps therefrom, and neutralizing the organic acidity of said oilwith caustic soda solution.

5. An improved process of neutralizing an acid treated oil of thelubricating type, which comprises substantially neutralizing the mineralacidity of said oil by an alkaline reagent without neutralizingsubstantially any of the organic acidity thereof, adding a demulsifyingcomposition adapted to settle out mineral salts and soaps from the oiland thereby removing salts and soaps produced in the neutralization, andneutralizing the organic acidity of said oil by an alkaline reagent.

6. An improved process of neutralizing an acid treated oil of thelubricating type, derived from a petroleum distillate of highneutralization number, which comprises substantially neutralizing themineral acidity of said oil without neutralizing substantially any ofthe organic acidity thereof by means of caustic soda solution, adding ademulsifying composition adapted to settle out mineral salts and soapsand thereby removing salts and-soaps produced in the neutralization, andneutralizing the organic acidity of said oil with caustic soda solution.

'7. An improved process of neutralizing an acid treated oil of thelubricating type, which comprises treating said oil with a. relativelyconcentrated caustic soda solution until about 80 to 90 per cent of themineral acidity has been neutralized, neutralizing the remaining mineralacidity with a relatively dilute caustic soda solution, adding ademulsifying composition adapted to settle out mineral salts and soapsand thereby removing salts and soaps produced in the neutralization, andneutralizing the organic acidity of said oil with caustic soda solution.

8. An improved process of neutralizing an acid treated oil of thelubricating type, derived from a petroleum distillate of highneutralization number, which comprises treating said oil with arelatively concentrated caustic soda solution until about 80 to 90' percent of the mineral acidity has been neutralized, neutralizing theremaining mineral acidity with a relatively dilute caustic sodasolution, adding a demulsiiying composition adapted to settle outmineral salts and soaps and thereby removing salts and soaps produced inthe neutralization, and neutralizing the organic acidity of said oilwith caustic soda solution.

9. An improved process of neutralizing an acid treated oil of thelubricating type, which comprises neutralizing said oil by an alkalinereagent substantially to the methyl orange end point, adding ademulsifying composition adapted to settle out mineral salts and soapsfrom the oil and thereby removing salts and soaps produced in theneutralization, and neutralizing th remaining acidity of said oil by analkaline reagent.

10. The process of claim 9, wherein said demulsifying composition isrosin soap.

ARTHUR E. CATANACH. ERIC KOLTHOFF.

